1. Technical Field
The present disclosure relates to orthopaedic prostheses, and more particularly, to stabilized tibial support structures for use with a knee prosthesis.
2. Description of the Related Art
Orthopaedic prostheses are commonly utilized to repair and/or replace damaged bone and tissue in the human body. For example, a knee prosthesis may be used to restore natural knee function by repairing damaged or diseased articular surfaces of the femur and/or tibia. Knee prostheses may include a femoral component implanted on the distal end of the femur, which articulates with a tibial component implanted on the proximal end of a tibia to replicate the function of a healthy natural knee.
One goal of knee replacement procedures is to reproduce or enhance the kinematics of the natural knee using the associated prosthetic components. More generally, such procedures seek to achieve kinematic characteristics that promote favorable patient outcomes such as minimized pain, proper joint function through a wide range of motion, and the longest possible prosthesis service life.
One aspect of establishing proper kinematics in a knee joint prosthesis is replication of the healthy natural “joint line” of the knee, i.e., the line spanning the medial and lateral points of contact between the femoral condyles and abutting tibial articular surfaces. To ensure that the natural joint line is preserved in the joint replacement procedure, the distal portion of the femur and the proximal portion of the tibia may each be resected by an amount corresponding to the thicknesses of the femoral and tibial components, respectively, such that the effective overall lengths of the femur and tibia remain unchanged after implantation of the prosthetic components.
However, in some cases the proximal tibia or distal femur may have severe degeneration, trauma, or other pathology which necessitates resection of more bone than can be compensated for by traditional femoral and tibial components. In such cases, augments may be used to effectively increase the thickness of the implanted component, thereby compensating for the additional thickness of the bone resection. Alternatively, a thicker prosthetic component can be employed instead of a component/augment combination.
In the proximal tibia, poor quality bone stock may also exist in the diaphyseal and/or metaphyseal region within the tibia. In such cases, a surgeon may opt for a second kind of augment, such as an augment having a generally cone-shaped outer profile corresponding to the generally cone-shaped bone defect typically encountered within the tibia. Exemplary tibial cone augments are disclosed in U.S. patent application Ser. No. 11/560,276, filed Nov. 15, 2006 and entitled PROSTHETIC IMPLANT SUPPORT STRUCTURE, and in U.S. patent application Ser. No. 12/886,297, filed Sep. 20, 2010 and entitled TIBIAL AUGMENTS FOR USE WITH KNEE JOINT PROSTHESES, METHOD OF IMPLANTING THE TIBIAL AUGMENT, AND ASSOCIATED TOOLS, both commonly assigned with the present application, the entire disclosures of which are hereby expressly incorporated by reference herein.
Where particularly acute degeneration of the proximal tibial bone stock has occurred, both a “cone” type augment and a “platform” type augment may be needed to i) replace resected bone stock within the tibia and ii) provide an elevated platform for a tibial baseplate component, respectively. In such cases, one or both of the augments may be cemented in place using bone cement, which adheres selected prosthetic knee components to one another and to the surrounding healthy bone stock. This bone cement may also be used join the pair of augments to one another, and to the tibial baseplate.
In some instances, such as where a knee prosthesis is implanted in a younger patient, a revision surgery may eventually become necessary to repair or replace damaged or worn out prosthesis components. Such revision surgery may require the removal and/or replacement of the tibial baseplate, which if cemented in place would typically be removed together with any augment components used in the previous surgery. Bone ingrowth into the material of the augment components may have occurred during the service life of the original prosthesis, possibly necessitating removal of additional healthy bone from the proximal tibia in order to fully dislodge the ingrown augment components.